Method and installation for applying foil material onto successive sheets

ABSTRACT

There is described a method for applying foil material onto successive sheets, especially sheets of securities. In a first step, individual sheets are transported in succession along a sheet transport path. In a second step, at least one continuous band of foil material is applied onto the individual sheets along a direction substantially parallel to a direction of displacement of the individual sheets, thereby forming a continuous flow of sheets linked to one another by the said at least one continuous band of foil material. In a third step, the said at least one continuous band of foil material is cut such that the continuous flow of sheets is again separated into individual sheets with portions of foil material remaining on the sheet. The cutting is performed at positions located on the sheets such that said portions of foil material remaining on the sheets do not extend beyond leading and trailing edges of the sheets. There is also described an installation for carrying out the above method.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/528,111, filed Aug. 21, 2009 now U.S. Pat. No. 7,922,858, which isthe National Stage of International Application No. PCT/IB2008/050626,filed Feb. 21, 2008, the entire disclosure of which is incorporatedherein by reference.

TECHNICAL FIELD

The present invention generally relates to a method and installation forapplying foil material onto successive sheets, especially sheets ofsecurities. The present invention is especially applicable in thecontext of the production of security documents, such as banknotes.

BACKGROUND OF THE INVENTION

The application of foil material onto sheets, especially sheets ofsecurities, is as such already well-known in the art. Such applicationis typically aimed at providing securities with additional securityelements, such as in particular so-called OVD's (Optically VariableDevices). OVD's typically take the form of a patch or foil laminatecomprising an optically-diffractive layer (usually a metalized layer)producing optically variable effects. OVD's are in particular knownunder the name of KINEGRAM®, which is a registered trademark of OVDKinegram AG, a member of the Leonhard Kurz Group.

OVD's are typically supplied in the form of a continuous film or band ofcarrier material carrying transfer elements that are to ultimately formthe actual OVD's. These are usually applied using so-called hot-foilstamping techniques, which make use of combined pressure and temperatureto activate an adhesive layer provided on the transfer elements andcause transfer thereof from the carrier material onto the sheets or webbeing processed.

Method and installations for carrying out hot-foil stamping techniquesare disclosed for instance in International applications nos. WO94/13487 A1, WO 97/01442 A1, WO 97/35721 A1, WO 97/35794 A1, WO 97/35795A1, WO 97/36756 A1, WO 03/043823 A1, WO 2005/102733 A2, and Europeanpatent application EP 0 965 446 A1.

Besides the application of OVD's on securities, it has also beenproposed to cut windows in the securities and cover these windows with afilm of foil material, usually transparent. Such a solution is forinstance proposed in International application no. WO 95/10420 A1. Incontrast to OVD's, the layer of foil material that is applied to coverwindows is comparatively thicker and more resistant as it has towithstand greater mechanical constraints and be self-supporting in theregion of the window.

Similarly, it has also been proposed to reinforce regions of reducedthickness created in securities by the provision of a film of foilmaterial onto said regions. A method for reinforcing security documentsprovided with at least one zone of reduced thickness is for instancedisclosed in International application no. WO 2004/024464 A1.

Provision of windows in securities can be carried out in different ways.A method and installation for cutting windows in sheets using mechanicalcutting tools is for instance disclosed in International application no.WO 03/092971 A1. A method and installation for cutting windows in sheetsusing a laser-cutting tool is for instance disclosed in Internationalapplication no. WO 2004/096482 A1.

Covering of the windows by foil material is discussed in greater detailin International applications nos. WO 2004/096541 A1 and WO 2005/068211A1.

According to International application no. WO 2004/096541 A1, foilmaterial is applied in the form of successive strips of foil materialthat are cut upstream of an application unit. The application unit isbasically similar to those used for carrying out hot-foil stamping withthe main difference that the strips of foil material are completelytransferred onto the sheets. In this context, it is more appropriate tosay that the application unit performs lamination of the foil materialonto the sheets, rather than stamping, which process involves transferof an element from a carrier band onto the sheets and recuperation ofthe used carrier band.

The solution of International application no. WO 2004/096541 A1 has beenfound to be rather difficult to implement as it requires precise cuttingand positioning of the cut strips of laminate with respect to thesheets. This prior art solution in particular requires aspecifically-designed aspiration system to properly seize and transportthe strips of laminate such that these are brought in contact with thesheets at the desired locations.

The solution of International application no. WO 2004/096541 A1 isfurthermore only applicable for strips of laminate having a minimumlength and is in particular not suited for applying small-sized patchesof foil material onto the sheets.

There is therefore a need for an improved method and installation forapplying foil material onto successive sheets.

SUMMARY OF THE INVENTION

A general aim of the invention is thus to improve the known methods andinstallations for applying foil material onto successive sheets.

An aim of the invention is in particular to provide a solution that isless complicated to implement than the known solutions.

A further aim of the present invention is to provide a solution thatallows application of foil material in a precise manner onto the sheets.

Still another aim of the present invention is to provide a solution thatallows application of foil material onto the sheets without thisaffecting further processing of the said sheets in the downstreamprocesses.

Yet another aim of the present invention is to provide a solution thatis capable of applying a wide range of sizes of portions of foilmaterial onto the sheets.

These aims are achieved thanks to the solution defined in the claims.

The method according to the invention comprises the following steps. Ina first step, individual sheets are transported in succession along asheet transport path. In a second step, at least one continuous band offoil material is applied onto the individual sheets along a directionsubstantially parallel to a direction of displacement of the individualsheets, thereby forming a continuous flow of sheets linked to oneanother by the said at least one continuous band of foil material. In athird step, the said at least one continuous band of foil material iscut such that the continuous flow of sheets is again separated intoindividual sheets with portions of foil material remaining on the sheet.Cutting of the said at least one continuous band of foil material isperformed at positions located on the sheets such that the portions offoil material remaining on the sheets do not extend beyond leading andtrailing edges of the sheets.

Thanks to the above method, a precise application of the foil materialonto the successive sheets is ensured, while guaranteeing that theapplied foil material does not cause perturbations during furtherprocessing of the sheets in the downstream processes. Indeed, as cuttingof the foil material is performed at positions located on the sheetssuch that the portions of foil material remaining on the sheets do notextend beyond the leading and trailing edges of the sheets, properalignment of the sheets in the downstream processes (which alignmentuses as reference the leading edge of the edge, or as the case may bethe trailing edge) is not affected.

A priori, cutting of the foil material at positions located on thesheets would appear to be detrimental to the integrity of the sheets.Tests have however shown that cutting of the foil material can becarried out on the surface of the sheets without any major problem.

Advantageous embodiments of the invention form the subject-matter of thedependent claims and are discussed below.

According to one embodiment of the invention, cutting can for instancebe performed by mechanical cutting tools without causing damage to thesheets. According to an alternate embodiment, and provided the foilmaterial is made of plastic or any other material that can be melted,cutting can be carried by melting the foil material using a heatingelement (such as a heated electrical wire). Still according to analternate embodiment, cutting of the foil material can be carried outusing a laser beam. Tests carried out by the Applicant have demonstratedthat laser cutting is in particular very efficient at selectivelycutting the foil material without damaging the sheets.

According to an advantageous embodiment, cutting of the said at leastone continuous band of foil material is performed immediately after aleading edge of the sheets and immediately before a trailing edge of thesheets over a whole width of the continuous band of foil material, suchthat a continuous portion of foil material is left remaining on eachsheet. In such case, it is in particular preferable to carry out cuttingin unprinted margins of the sheets.

According to an alternate embodiment, cutting of the said at least onecontinuous band of foil material is performed at a plurality oflocations along a length of the continuous band of foil material, suchthat a plurality of distinct portions of foil material are leftremaining on each sheet. In such case, the plurality of distinctportions remaining on the sheets can have a width smaller than a widthof the continuous band of foil material, the remaining portions of thecontinuous band of foil material that is not to remain on the sheetsforming a contiguous band of material that can be recuperated, forinstance by winding around a recuperating roll.

Still according to an advantageous embodiment, the remaining portions ofthe continuous band or bands of foil material that are not to remain onthe sheets are evacuated, preferably by aspiration.

In the context of the invention, the continuous band or bands of foilmaterial can advantageously be supplied in the form of a roll of foilmaterial.

In the context of the production of documents, such as securitydocuments, wherein the sheets each carry an array of imprints arrangedin a matrix of rows and columns, at least one continuous band of foilmaterial is applied along each column of imprints.

The present invention is in particular applicable to cover windows oropenings cut into the sheets prior to the application of the continuousband or bands of foil material. In this case in particular, it isadvantageous to apply a foil material that is substantially transparent.

The foil material is preferably a plastic laminate comprising anadhesive layer which is brought into contact with the surface of thesheets. This adhesive layer is advantageously a pressure-activatedand/or thermo-activated adhesive layer which is activated duringapplication only at locations corresponding to the portions of foilmaterial that are to remain on the sheets. Cutting is preferably carriedout in this case at locations where the adhesive layer has not beenactivated, advantageously in an immediate vicinity of the portions offoil material that are to remain on the sheets. In this case, whileperipheral portions of the foil material are not adhering to the sheetsafter the application process, the dimensions thereof can be minimized.Furthermore, it is common practice to subject the sheets afterapplication of foil material to an intaglio printing process, especiallyin order to overprint the foil material. As a result of intaglioprinting, the peripheral portions of the foil material are made toadhere to the sheets due to the combined effect of temperature andpressure inherent to intaglio printing.

An installation for carrying out the above method forms thesubject-matter of dependent claims, which installation generallycomprises:

-   -   a sheet-by-sheet feeding station for feeding the individual        sheets;    -   a foil application unit for applying the said at least one        continuous band of foil material onto the individual sheets;    -   cutting unit, located downstream of the foil application unit,        for cutting the said at least one continuous band of foil        material; and    -   a sheet delivery station for receiving the individual sheets.

According to a preferred embodiment of the installation, the cuttingunit comprises a cutting cylinder carrying at least one cutting tool onits outer circumference, which cutting cylinder is rotated insynchronism with the sheets. This cutting cylinder preferably comprisesat least one cutting blade for mechanically cutting the continuous bandof foil material or a heating element for cutting the continuous band offoil material by melting. A temperature of the cutting cylinder canfurthermore advantageously be regulated so as to prevent dilatation ofthe cutting cylinder which could affect the accuracy of the cuttingoperations.

According to an alternate embodiment, a laser cutting tool can be usedto perform the cutting operation.

The installation is advantageously further provided with means forevacuating remaining portions of the continuous band of foil materialthat are not to remain of the sheets, preferably by aspiration. A devicefor checking that these remaining portions are properly being evacuatedis preferably further provided.

According to still another preferred embodiment of the installation,means are further provided for checking passage of a leading and/ortrailing edge of the sheets and adjusting operation of the cutting unitas a function of the passage of the leading and/or trailing edge of thesheets. This ensures a stable operation and precise cutting of the foilmaterial at determined locations on each sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will appear moreclearly from reading the following detailed description of embodimentsof the invention which are presented solely by way of non-restrictiveexamples and illustrated by the attached drawings in which:

FIG. 1 is a schematic side view of a sheet-fed processing machine forapplying foil material onto successive sheets according to oneembodiment of the invention;

FIG. 2 is a schematic top view of two successive sheets linked to oneanother by a plurality of continuous bands of foil material which areapplied onto the sheets along a direction parallel to a direction ofdisplacement of the sheets;

FIG. 3 is a schematic top view of a single sheet after cutting of theplurality of continuous bands of foil material of FIG. 2;

FIGS. 4A to 4E are schematic side views illustrating operation of acutting cylinder used as a cutting unit for cutting the foil materialaccording to one variant of the invention;

FIG. 5 is a schematic front view of a cutting arrangement of the cuttingcylinder of FIGS. 4A to 4E;

FIG. 6 is a schematic top view of a single sheet after cutting of theplurality of continuous bands of foil material of FIG. 2 according to avariant of the invention; and

FIGS. 7A and 7B are partial top views of a band of foil materialillustrating possible cutting alternatives of the band of foil material.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1 is a schematic side view of a sheet-fed processing machine forapplying foil material onto successive sheets according to oneembodiment of the invention. The configuration thereof is almostidentical to the hot-foil stamping machines of the prior art, as forinstance disclosed in International applications nos. WO 97/35721 A1, WO97/35794 A1, WO 97/35795 A1 and WO 97/36756 A1, the disclosures of whichare incorporated herein by reference. It comprises a sheet-by-sheetfeeding station 1 for feeding individual sheets S to a foil applicationunit 2, which foil application unit 2 basically comprises an applicationcylinder 21 (in this case a four-segment cylinder having four segmentseach capable of seizing and transporting a sheet coming from thesheet-by-sheet feeding station 1) that cooperates with a plurality ofrows of pressure rollers 22 which are pressed resiliently against thecircumference of the application cylinder 21 by means of pneumaticcylinders (not referenced). In this case, three pairs of rows ofpressure rollers 22 are pressed against the circumference of theapplication cylinder 21.

Foil material is supplied from a supply roll 20 in the form of acontinuous band of foil material 200. This continuous band 200 is fed tothe application cylinder 21 so as to be sandwiched between thecircumference of the application cylinder 21 and the sheets S. In thecontext of the production of security documents, such as banknotes, eachsheet S is typically provided with an array of imprints P arranged in amatrix of rows and columns (as is for instance illustrated in FIGS. 2and 3). One will thus understand that at least one supply roll 20 willbe provided so as to supply a corresponding band of foil material 200along each column of imprints P.

The foil material 200 is preferably made of a plastic laminate,preferably substantially transparent, such as, but not limited to, apolyester (PET) or polycarbonate (PC) material, comprising an adhesivelayer which is brought into contact with the surface of the sheets. Thisfoil material 200 can optionally be provided with a partiallydemetallized layer as for instance sold under the name of KINEGRAMZero.Zero®, which is a registered trademark of OVD Kinegram AG.

The adhesive layer is preferably a pressure-activated and/ortemperature-activated adhesive layer which is activated duringapplication only at locations corresponding to the portions of foilmaterial that are to remain on the sheets. Alternatively, a two-compoundadhesive could be used wherein one adhesive compound is applied on thefoil material and the other adhesive compound is applied onto the sheetsprior to foil application (such as discussed for instance inInternational application no. WO 2005/068211 A1).

The application cylinder 21 is provided with a plurality of heatedstamping members (not shown) at the locations where the foil material200 is to be applied onto the sheets S. International application no. WO2005/102733 A2, the disclosure of which is incorporated herein byreference, provides a detailed description of an application cylinder 21equipped with such stamping members. It suffice to understand that thestamping members are dimensioned according to the portions of adhesivelayer to be activated on the foil material 200 and that the pressurerollers 22 are designed for rolling contact with the said stampingmembers.

For instance, in the context of the embodiment illustrated by FIGS. 2and 3, which embodiment will be discussed below, it is envisaged toapply each continuous band of foil material 200 so that a continuousportion thereof, designated by reference numeral 200*, is left remainingon each sheet S. In other words, each stamping member on the applicationcylinder 21 is dimensioned such as to exhibit the shape of a strip thelength of which corresponds to the length of adhesive layer to beactivated on the band of foil material 200.

Following application of the continuous bands of foil material 200 ontothe individual sheets S, a continuous flow of sheets S linked to oneanother by the continuous bands of foil material 200 is formed, asschematically illustrated in FIG. 2.

Referring again to FIG. 1, the continuous flow of sheets S linked by thecontinuous bands of foil material 200 is fed to a cooling unitcomprising a cooling roller 23 cooperating with conveyor belts 24. Inthe illustrated embodiment, the conveyor belts 24 are driven intorotation so as to turn in a counter-clockwise direction in FIG. 1 anddraw the continuous flow of sheets S away from the surface of theapplication cylinder 21, against the circumference of the cooling roller23 (which roller 23 rotates in the clockwise direction in FIG. 1), andonto a horizontal guide plate 25.

The cooling unit is not as such required and may be omitted. Tests havehowever shown that the cooling unit may be advantageous in that itenables stabilization and regulation of the temperature of the processedsheets S as well as of the downstream portion of the foil applicationunit 2 where the cutting unit, designated by reference numeral 5, islocated.

The cutting unit 5, to be described in greater detail hereinafter, islocated downstream of the foil application unit 2, in the vicinity ofthe horizontal guide plate 25, for cutting the continuous bands of foilmaterial 200.

As a result of this cutting, the continuous flow of sheets S is againseparated into individual sheets S with portions of foil material,designated by reference numeral 200* in FIG. 3, remaining on the sheetsS. Such separation is necessary as the sheets S are to be transferred toa downstream-located chain conveyor system, designated generally byreference numeral 3 in FIG. 1.

As illustrated in FIG. 1, a suction drum 26 is located below theconveyor belts 24, downstream of the guide plate 25 and of the cuttingunit 5. The circumferential surface of the suction drum 26 is tangentupon the plane in which the sheets S are conveyed in this region. Thesuction drum 26 preferably has a dedicated speed-controllable and/orposition-controllable drive (not shown), comprising for instance anelectric motor the speed of which can be adjusted. A circumferentialspeed of the suction drum 26 is controlled in such a manner that thesuction drum 26 is initially at the conveying speed of the conveyorbelts 24, is then accelerated to a speed which is slightly greater thanthe speed of the chain conveyor system 3, and is then decelerated againin order to permit transfer of the sheet S with which the suction drum26 cooperates to a corresponding one of the gripper bars 30 of the chainconveyor system 3. This “overspeed” is required in order to cover anecessary travel of the sheet S between suction drum 26 and chainconveyor system 3.

Once transferred to the chain conveyor system 3, the processed sheetsare then conveyed to a delivery pile unit of a sheet delivery station 4.

FIG. 2 is a schematic illustration of the flow of sheets S as it wouldbe formed as a result of the application of the continuous bands of foilmaterial 200 downstream of the application cylinder 21 in FIG. 1. InFIG. 2, reference numeral 100 designates windows that have been providedin the sheets S prior to the application of the continuous bands of foilmaterial 200. Such windows 100 might be provided on-line in the sameprocessing machine where the foil material 200 is applied (as forinstance proposed in International application no. WO 2004/096541 A1) orin a separate machine.

In FIG. 2, which illustrates sheets S each carrying an array of imprintsP arranged in eight rows and five columns (which matrix arrangement ispurely illustrative), five continuous bands of foil material 200 areapplied along a direction parallel to the sheet transport direction(indicated by the vertical arrows in FIG. 2), i.e. one continuous band200 per column of imprints P. It shall be appreciated that more than onecontinuous band of foil material 200 could be applied per column ofimprints P, for instance in case windows 100 are provided at more thanone location along the length (i.e. transversely to the sheet transportdirection) of each imprint P. In the illustrated example, each imprint Pis provided with two windows 100 that are covered by the same band offoil material 200.

In FIG. 2, references lm and tm respectively designate a leading marginand trailing margin of the sheets S, i.e. portions of the sheets that donot carry any imprint P. While these margins will also be referred to as“unprinted margins”, it shall be understood that such margins couldnevertheless be provided with printed markings, for instance markingsthat are exploited in the context of logistic and/or quality managementof the sheets.

In FIG. 2, the dashed lines designated by references C1 and C2 at thetrailing and leading portions of the sheets, respectively, areindicative of the locations where cutting operations are to be carriedout in the context of this first embodiment. In other words, accordingto this first embodiment, the continuous bands of foil material 200 arecut immediately after a leading edge of the sheets S (more preciselywithin the unprinted leading margin lm) and immediately before atrailing edge of the sheets S (more precisely within the unprintedtrailing margin tm) over a whole width of the continuous bands 200. As aresult, as illustrated by FIG. 3, continuous portions of foil material,which portions are designated by reference numerals 200*, are leftremaining on each sheet S.

FIGS. 4A to 4E are schematic side views illustrating operation of thecutting unit 5 of FIG. 1 to perform cutting of the foil material in themanner illustrated in FIGS. 2 and 3.

According to this embodiment of the invention, the cutting unit 5preferably comprises a cutting cylinder 50 carrying a cutting tool 51 onits outer circumference, which cutting cylinder 50 is rotated insynchronism with the sheets S. In this example, the cutting tool 51comprises a pair of cutting blades that extend transversely to thelength of the continuous band of foil material 200, as illustrated inFIG. 5. Between the cutting blades of the cutting tool 51 there ispreferably provided a suction portion 52 with suction apertures 52 a thepurpose of which will be described hereinafter.

The cutting blades of the cutting tool 51 could alternatively bereplaced by a pair of heating elements (such as electrical wires)designed to perform cutting of the bands of foil material 200 bymelting, provided the foil material is a material that can be melted,such as a plastic material.

According to this embodiment, one will appreciate that the shortestdistance between the two cutting blades of the cutting tool 51 (i.e. thedistance where the suction portion 52 is located) corresponds to thedistance between the cutting line C1 depicted in FIG. 2 in the trailingmargin tm of a preceding sheet and the cutting line C2 in the leadingmargin lm of a subsequent sheet. Such distance will depend on the actualdistance between two successive sheets and the actual positions wherethe cutting operations are to be carried out on the sheets. Accordingly,it might be advantageous to design the cutting cylinder 50 such that adistance between the cutting blades of the cutting tool 51 isadjustable.

A temperature of the cutting cylinder could advantageously be regulatedso as to avoid modification of the distance between the cutting bladesof the cutting tool 51 due to dilatation of the cylinder 50.

One will also appreciate that, in case the cutting cylinder 50 isrotated at a substantially constant speed together with the sheets S,the circumference of the cutting cylinder 50 should be such that iscorresponds to the periodic distance between two successive sheets.

It is advantageous to provide the cutting cylinder 50 with its ownspeed-controllable and/or position-controllable drive so that adjustmentof the angular position of the cutting cylinder 50 can be performed onthe fly to ensure proper positioning of the cutting tool 51 with respectto the sheets and the bands of foil material 200.

FIG. 4A illustrates the cutting cylinder 50 positioned at a timecorresponding to cutting of the bands of foil material 200 along thecutting line C1 depicted in FIG. 2, i.e. at the trailing portion of asheet. In this situation, the first cutting blade of the cutting tool 51is brought in contact with the foil material 200 applied on the sheet S,causing cutting thereof. A supporting member 55 is preferably providedon the opposite side of the sheet S as illustrated in FIG. 4A so as toprovide a proper reference surface to support the sheet S and ensure aclean cutting of the band of foil material 200. The distance of thesupporting member 55 with respect to the cutting blades of the cuttingtool 51 is preferably adjustable. Following the cutting operationdepicted in FIG. 4A, one will understand that portions 200* of the bandsof foil material 200 are cut loose, thereby freeing the associated sheetS which can then be seized and transferred to the downstream-locatedchain conveyor system 3, as discussed hereinabove.

FIG. 4B illustrates a subsequent stage of the processing where thecutting cylinder 50 has been rotated clockwise by a few degrees, therebybringing the second cutting blade of the cutting tool 51 in contact withthe leading portion of the subsequent sheet S which is transported underthe cutting cylinder 50, i.e. the position corresponding to the secondcutting line C2 depicted in FIG. 2.

Following the cutting operation illustrated in FIG. 4B, a small portionof foil material, designated by reference numeral 205, is cut andseparated from the remainder of the band of foil material 200. Thissmall portion 205 is aspirated by the suction portion 52 so as to becarried and evacuated by further rotation of the cutting cylinder 50.

FIG. 4C illustrates a subsequent stage of the processing where thecutting cylinder 50 has been further rotated clockwise by almost ninetydegrees, thereby bringing the cutting tool 51 in front of a device 61,the purpose of which is to check for the presence of the small portionof foil material 205 that is being evacuated. This device 61 can be asimple light-emitting device directed towards the surface of the cuttingcylinder 50 with a photoreceptor for checking a reflection point of thelight beam produced by the light-emitting device. The device 61 couldalternatively be a camera for taking a whole picture of the portion offoil material 205 held onto the suction portion 52.

By checking for the presence of the small portion of foil material 205on the suction portion 52 of the cutting tool 51, one can ensure thatthe portion 205 is properly being evacuated and is not falling down ontothe sheets, which could affect the quality of the processed sheetsand/or interfere with the operation of the machine. This control alsoprovides an indication of whether or not the cutting operation wasproperly carried out.

FIG. 4D illustrates still a subsequent stage of the processing where thecutting cylinder 50 has been further rotated clockwise again byapproximately ninety degrees, thereby bringing the cutting tool 51 infront of an evacuation system 53 for evacuating the portion of foilmaterial 205, preferably by aspiration. In this position, the operationof the suction portion 52 is interrupted such as to permit aspirationand evacuation of the portion of foil material 205 in the evacuationsystem 53.

FIG. 4E illustrates yet another subsequent stage of the processing wherethe cutting cylinder 50 has been further rotated clockwise. In theillustrated situation, the leading edge of a subsequent sheet Scoincides with the intersection point of a light beam generated by asecond device 62, the purpose of which is to detect the passage of theleading edge of the sheets S. This can be performed by monitoring areflection point of the light beam generated by the device 62 on thesurface of the sheets or by positioning a photoreceptor on the otherside of the sheets such as to detect interruption of the light beamcaused by passage of the sheets S. The purpose of this detection is toprovide an indication of the passage of the sheets and enablesadjustment of the operation of the cutting unit 5. More precisely, inthe illustrated embodiment, detection of the passage of the leading edgeof the sheets S can be used to correct the rotation of the cuttingcylinder 50 and ensure that the cutting tool 51 is brought in contactwith the sheets and foil material 200 at the appropriate time.

It will of course be understood that one could alternatively detectpassage of the trailing edge of the sheets. Still according to analternate embodiment, one could detect both the passage of the trailingedge of a preceding sheet and the leading edge of a subsequent sheet tothereby provide an indication of the actual distance between twosuccessive sheets S.

Within the scope of the present invention, one could alternatively use alaser-cutting unit to cut the continuous band of foil material 200. Thiswould not necessitate a cylinder as illustrated.

Still according to an alternate embodiment of the invention, one couldcut the continuous bands of foil material 200 at a plurality oflocations along the length of the foil material, such that a pluralityof distinct portions of foil material 200* are left remaining in eachcolumn of imprints P on the sheets, as for instance illustrated in FIG.6. This is useful in case one wishes to avoid that the foil material200* extends over the whole height of each imprint P, and be limited toonly a small region surrounding the windows 100. One will appreciatethat this would require a greater number of cutting operations persheet. This could for instance be performed by using a correspondingnumber of cutting tools 51 (whether cutting blades or heating elements)along the circumference of the cutting cylinder 50 (or by appropriatelyoperating a laser-cutting unit).

In order to produce the result of FIG. 6, the cutting operations couldbe carried out over the whole width of the continuous band of foilmaterial 200 as illustrated in FIG. 7A, thereby creating an alternatesuccession of portions 200* that are to remain on the sheets S andremaining portions 205 that are to be evacuated. Alternatively, theportions of foil material 200* that are to remain on the sheets S couldbe cut into the continuous band of foil material 200, as illustrated inFIG. 7B, so as to leave a continuous band of foil material 205 that canbe evacuated by simply winding this continuous band 205 around anevacuation roll (which would not accordingly require aspiration means toevacuate the remaining portion of the foil material). In this lattercase, one will understand that the distinct portions of foil material200* remaining on the sheets S have a width smaller than the width ofthe continuous band of foil material 200.

In the context of the present invention, cutting is preferably carriedout at locations where the adhesive layer has not been activated,preferably in an immediate vicinity of the portions of foil materialthat are to remain on the sheets. While peripheral portions of the foilmaterial are not adhering to the sheets after the application process insuch a case, the dimensions thereof can be minimized. Furthermore, it iscommon practice to subject the sheets after application of foil materialto an intaglio printing process, especially in order to overprint thefoil material. As a result of intaglio printing, the peripheral portionsof the foil material are made to adhere to the sheets due to thecombined effect of temperature and pressure inherent to intaglioprinting.

Various modifications and/or improvements may be made to theabove-described embodiments without departing from the scope of theinvention as defined by the annexed claims. For instance, as alreadymentioned, a cutting cylinder is not as such required but constitutes apreferred solution for carrying out the cutting operations using, forexample, a mechanical cutting tool. Within the scope of the presentinvention, any cutting unit could be used as long as it can carry outcutting of the foil material onto the sheets.

It shall furthermore be appreciated that, while the invention ispreferably applied with a view to cover windows cut into the sheets, theinvention is equally applicable to any other situation where one wishesto apply foil material onto the sheets by lamination, rather than byhot-foil stamping techniques. In particular, the invention could also beapplied in the context of the reinforcement of regions of reducedthickness, such as discussed in WO 2004/024464 A1.

Lastly, it might be advantageous to provide an inspection systemdownstream of the cutting unit for inspecting the quality of the sheetsand detecting defects on the sheets, such as improperly cut foilmaterial and/or remaining portions of foil material sticking to thesheets, as the case may be.

The invention claimed is:
 1. A method for applying foil material ontosuccessive sheets, comprising the steps of: transporting individualsheets in succession along a sheet transport path, which individualsheets are not linked to one another; applying at least one continuousband of foil material onto the individual sheets along a directionsubstantially parallel to a direction of displacement of said individualsheets, thereby forming a continuous flow of sheets linked to oneanother by said at least one continuous band of foil material; andcutting said at least one continuous band of foil material such thatsaid continuous flow of sheets is separated into the individual sheetswhich are not linked to one another with portions of foil materialremaining on the sheets, whereby the cutting is performed at positionslocated on said sheets without cutting through the sheets and such thatsaid portions of foil material remaining on the sheets do not extendbeyond leading and trailing edges of the sheets.
 2. The method accordingto claim 1, wherein said at least one continuous band of foil materialis cut immediately after a leading edge of the sheets and immediatelybefore a trailing edge of the sheets over a whole width of said at leastone continuous band of foil material, such that a continuous portion offoil material is left remaining on each said sheet.
 3. The methodaccording to claim 2, wherein cutting is performed in unprinted marginsof the sheets.
 4. The method according to claim 1, wherein said at leastone continuous band of foil material is cut at a plurality of locationsalong a length of said at least one continuous band of foil material,such that a plurality of distinct portions of foil material are leftremaining on each said sheet.
 5. The method according to claim 4,wherein said plurality of distinct portions of foil material remainingon the sheets have a width smaller than a width of said at least onecontinuous band of foil material and wherein a remaining portion of saidat least one continuous band of foil material is recuperated.
 6. Themethod according to claim 2, wherein portions of said at least onecontinuous band of foil material that are not to remain on the sheetsare evacuated.
 7. The method according to claim 1, wherein said at leastone continuous band of foil material is supplied in the form of a rollof foil material.
 8. The method according to claim 1, wherein saidsheets are sheets carrying an array of imprints arranged in a matrix ofrows and columns, and wherein at least one continuous band of foilmaterial is applied along each column of imprints.
 9. The methodaccording to claim 1, further comprising the step of cutting windowsinto said sheets prior to the application of the said at least onecontinuous band of foil material, which windows are covered by said atleast one continuous band of foil material.
 10. The method according toclaim 1, wherein said at least one continuous band of foil material issubstantially transparent.
 11. The method according to claim 1, whereinsaid at least one continuous band of foil material is a plastic laminatecomprising an adhesive layer which is brought into contact with thesurface of the sheets.
 12. The method according to claim 11, whereinsaid adhesive layer is a pressure-activated and/or thermo-activatedadhesive layer which is activated during application only at locationscorresponding to the portions of foil material that are to remain on thesheets.
 13. The method according to claim 12, wherein cutting of saidcontinuous band of foil material is performed at locations where theadhesive layer has not been activated.
 14. An installation for applyingfoil material onto successive sheets, comprising: a sheet-by-sheetfeeding station for feeding individual sheets in succession along asheet transport path, which individual sheets are not linked to oneanother; a foil application unit for applying at least one continuousband of foil material onto said individual sheets along a directionsubstantially parallel to a direction of displacement of the individualsheets, thereby forming a continuous flow of sheets linked to oneanother by said at least one continuous band of foil material; a cuttingunit, located downstream of said foil application unit, for cutting saidat least one continuous band of foil material such that the continuousflow of sheets is separated into the individual sheets which are notlinked to one another with portions of foil material remaining on thesheets, whereby the cutting unit is performing the cutting at positionslocated on a surface of the sheets without causing damage to the sheetsand such that the portions of foil material remaining on the sheets donot extend up to nor beyond leading and trailing edges of the sheets;and a sheet delivery station for receiving the individual sheets. 15.The installation according to claim 14, wherein said cutting unitcomprises a cutting cylinder carrying at least one cutting tool on itsouter circumference.
 16. The installation according to claim 15, whereinsaid at least one cutting tool comprises at least one cutting blade formechanically cutting the continuous band of foil material or a heatingelement for cutting the continuous band of foil material by melting. 17.The installation according to claim 15, wherein a temperature of saidcutting cylinder is regulated.
 18. The installation according to claim14, wherein said cutting unit comprises a laser cutting tool.
 19. Theinstallation according to claim 14, further comprising means forevacuating portions of the continuous band of foil material that are notto remain on the sheets.
 20. The installation according to claim 19,further comprising a device for checking that the portions are properlybeing evacuated.
 21. The installation according to claim 14, furthercomprising means for checking passage of a leading and/or trailing edgeof the sheets and adjusting operation of the cutting unit as a functionof the passage of the leading and/or trailing edge of the sheets. 22.The method according to claim 4, wherein portions of said at least onecontinuous band of foil material that are not to remain on the sheetsare evacuated.
 23. The installation according to claim 16, wherein atemperature of said cutting cylinder is regulated.
 24. The methodaccording to claim 1, wherein the successive sheets are sheets ofsecurities.
 25. The method according to claim 6, wherein the portions ofsaid at least one continuous band of foil material that are not toremain on the sheets are evacuated by aspiration.
 26. The methodaccording to claim 13, wherein cutting of said continuous band of foilmaterial is performed in an immediate vicinity of the portions of foilmaterial that are to remain on the sheets.
 27. The installationaccording to claim 19, wherein said means evacuate the portions of saidat least one continuous band of foil material that are not to remain onthe sheets by aspiration.
 28. The method according to claim 22, whereinthe portions of said at least one continuous band of foil material thatare not to remain on the sheets are evacuated by aspiration.